The invention relates to a device and a method for feeding bulk material items from a mass multiply arranged one above the other in a store into a randomly re-alignable, individually distributed and disentangled position within the reach of a robot, the device comprising a substantially horizontally arranged oscillating conveyor surface with means for the forward feed or reverse transport of the bulk material items in the x-direction or in the x- and y-direction of the space coordinates, means for exciting an at least partial oscillation of the oscillating conveyor surface in the z-direction of the space coordinates, a vision system with a camera or a sensor for individual detection of the number, position and alignment of the individual bulk material items, and a processor for processing the sensor signals and generating control commands to actuators.
In the industrial production and fitting of consumer goods, more or less complicated mass-produced parts are frequently provided in bulk material form for further processing. For the following processing and/or fitting operations, the bulk material items are required to be disentangled, separated and in a position which is aligned in a defined manner. Vibrating spiral conveyors, in which mechanical baffles are provided along a conveyor spiral, are often used for this purpose. These align the bulk material items along their conveying direction or eliminate them so that only correctly aligned bulk material items arrive at the discharge site. An additional mechanical apparatus can arrange the separation and fine positioning of the bulk material items which can be controlled and removed by a handling system or a robot owing to these preparatory operations.
The arrangement and design of baffles has to be specifically optimised for each type of bulk material item. The flexibility of the spiral conveyor has been further improved in the last 10 to 15 years by the use of active baffles (sensor/actuator) and replaceable baffles/positioning stations but these cannot yet meet the current demands from industry for flexible self-correcting feeds which can be programmed for different bulk material items.
A plurality of known flexible feed systems consist of one unit which mechanically processes the bulk material items such that they are recognised by a vision system known as an image processing system (machine vision) and can be removed by a robot. Bulk material items which are not recognised migrate back into the provided bulk material and reappear at a later instant.
In a known device for flexibly feeding bulk material items 12 according to FIG. 1, these are partially processed in a store 14. The bulk material items 12 leave the store 14 on a conveyor surface 16 and migrate in the direction of a robot 18 with a pivoting arm 20, which has a gripper tool 24 for bulk material items 12, which can be rotated about this shaft 22 and is fastened at the end face to a height-adjustable shaft 22.
A camera 26 determines, in a selection zone 28 which is shown by dotted lines, the exact position of the bulk material items 12 in the desired preferred position. With the aid of transmitted data, a robot controller 30 calculates the coordinates and correspondingly triggers the actuators of the robot 18, which grasps the bulk material items 12 that are arranged in the mentioned desired preferred position, in the speed of seconds. The removed bulk material items 12 are placed on a conveyor belt 34 and supplied for further processing and this is indicated by an arrow 32.
The bulk material items 12 which are not grasped by the robot 18, on the other hand, are recycled in the store 14 and guided again in random arrangement into the selection zone 28 by way of the conveyor surface 16 with further bulk material items 12 stored in the store.
All the bulk material items 12 contained in the store 14 have to be replaced at periodic intervals, so defective bulk material items 12 do not remain in constant rotation.
U.S. Pat. No. 5,687,831 describes a device for feeding bulk material items, which contains a substantially horizontal conveyor surface. The bulk material items are transported to a selection zone, where the arranged and aligned bulk material items are located by means of a video camera, grasped by a robot and transferred to a fitting system. The bulk material items which are not removed are guided back to the beginning of the conveyor surface by means of a recirculation system for a renewed passage. During the return, the position and alignment of the bulk material items is changed such that they are aligned as favourably as possible during the next passage and can possibly be selected and removed in the selection zone. The device according to U.S. Pat. No. 5,687,831 can probably process a wide variety of bulk material item shapes but it is constructionally relatively complex and requires a substantial overall volume for the arrangement of the conveying surface, the selection zone and the recirculation system.
In a device for flexibly feeding bulk material items according to U.S. Pat. No. 6,056,108, a flexible membrane is arranged for the transport of flexible bulk material items, on which membrane a selection zone is defined. In this region, the position of the bulk material items is analysed by a mechanical vision system. The sensor signals are converted in a processor to control commands which selectively trigger the transmission of a pulse to specific points of the flexible membrane, so the position of at least some bulk material items is changed in the selection zone and is brought into a desired positive alignment. These bulk material items with the desired alignment are selected and removed from the membrane by a robot.
A feed device for the bulk material items to a robot according to WO,A1 00/69240 comprises a selection zone of an apparatus which is accessible to the robot for randomly changing the position and/or alignment and an apparatus with a parts recirculation element for recirculating the bulk material items which are not grasped. The apparatus for randomly changing the position and/or alignment of the bulk material items is a vibration platform simultaneously designed as a selection zone. In a first relative position of the recirculation element and vibration platform, the platform can be loaded with bulk material items of the recirculation element. In a second relative position, the bulk material items which drop from the vibration platform can be caught by the recirculation element. During operation of the device for feeding bulk material items for a robot, at least six steps are carried out one after the other in a continuous endless process. In a first step, the vibration platform is loaded with bulk material items from the parts recirculation element. In a second step, bulk material items dropping from the vibration platform are caught by the recirculation element. In a third step, the position and/or alignment of the bulk material items on the vibration platform is randomly changed. In a fourth step, the position and alignment of the bulk material items is detected and the data transmitted to the robot, which in a fifth step grasps bulk material items in a favourable position and alignment and conveys them away. In a sixth step, the number of bulk material items remaining on the vibration platform is determined and depending on the result, returned to the first or second step.
The object of the present invention is to provide a device and a method of which Improve and simplify the feeding of bulk material items from a store to a robot.